Shant Baghram

Department of Physics, Sharif University of Technology,

Research Center for High Energy Physics, Department of Physics, Sharif University of Technology

In Search of Extraterrestrial Artificial Intelligence Through Dyson Sphere–like Structures around Primordial Black Holes*

Abstract: Are we alone? It is a compelling question that human beings have confronted for centuries. The search for extraterrestrial life is a broad range of quests for finding simple forms of life up to intelligent beings in the Universe. The plausible assumption is that there is a chance that intelligent life will be followed by advanced civilization equipped or even dominated by artificial intelligence (AI). In this work, we categorize advanced civilizations (on an equal footing, an AI-dominated civilization) on the Kardashev scale. We propose a new scale known as the space exploration distance to measure civilization advancement. We propose a relation between this length and the Kardashev scale. Then, we suggest the idea that advanced civilizations will use primordial black holes (PBHs) as sources of harvesting energy. We calculate the energy harvested by calculating the space exploration distance. Finally, we propose an observational method to detect the possibility of extraterrestrial AI using Dyson sphere–like structures around PBHs in the Milky Way and other galaxies. (Based on Shant Baghram, 2025 ApJ 978 132)

*This work is dedicated to Sohrab Rahvar, whom we admire for first teaching us about life in the Universe.

یکشنبه 12 اسفند 1403، ساعت 15:00

Sunday 2 March 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی­تئاتر – تالار جناب /Physics Department – Amphitheatre– Jenab Hall   

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Elahe Khalouei

Astronomy Research Center, Research Institute of Basic Sciences, Seoul National University

Multi-Messenger Research at the Center for the Gravitational-Wave Universe

Abstract: In this presentation, we will begin with a brief review of South Korea’s in-kind contributions to major projects such as LSST and SPHEREx, as well as their plans to develop a multi-system telescope for future competition (~ 6 min).

 Next, we will cover the following topics:

1-    The observation of strongly lensed supernovae using a 7-dimensional telescope (~20 min).

2-    Key definitions related to gravitational waves (~10 min).

3-    If time permits, the application of deep learning in gravitational wave studies (~10 min).

یکشنبه 5 اسفند 1403، ساعت 15:00

Sunday 23 February 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی­ تئاتر – تالار جناب /Physics Department – Amphitheatre– Jenab Hall   

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Mohammad Hossein Namdar

Department of Physics, Sharif University of Technology

Cosmological Structure Formation in Monge-Ampère Gravity 

Abstract: The Monge-Ampère gravity is a novel and effective mathematical theory in the formation of cosmic structures, proposed with the aim of generalizing classical Newtonian gravity. This theory is based on the Monge-Ampère equation, a nonlinear version of the Poisson equation that relates the determinant of the Hessian of the potential to the density field. We precisely demonstrate how the Poisson equation can be derived from the Monge-Ampère equation in the weak field limit. Subsequently, we analytically solve the equation for a point mass density distribution under the assumption of spherical symmetry. We further investigate structure formation in the presence of this gravity and determine the critical density required for structure formation using the spherical collapse approximation in both linear and nonlinear regimes. Finally, we examine the statistics of the halos formed under this gravity. Although we consider Monge-Ampère gravity as an effective rather than a fundamental theory in this study, we compare our results with the solutions of the Poisson equation in all cases.

یکشنبه 28 بهمن 1403، ساعت 15:00

Sunday 16 February 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی ­تئاتر – تالار جناب Physics Department – Amphitheatre– Jenab Hall  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Zeinab Kalantari

Department of Physics, Sharif University of Technology,

Research Center for High Energy Physics, Department of Physics, Sharif University of Technology

A Study of Cosmological Models Based on Long Gamma-ray Bursts Duration Histogram

Abstract: In this presentation, I want to speak about the idea of constraining the cosmological model by the long GRBs’ duration data of the Swift-BAT satellite. Gamma-ray bursts’ powerful luminosity enables us to explore the universe at the farthest redshift reaches ever explored. The maximum observable redshift of gamma-ray bursts is estimated to be around $z=9.4$, so GRBs could serve as an excellent tool to investigate the characteristics of the cosmos at high redshifts, such as constraining the cosmological parameters such as dark energy equation of state. The burst duration $T_{90}$ is a significant property of GRBs that can be analyzed. In my presentation, I focus on comparing the histogram of long GRBs’ duration resulting from a kind of $ \omega CDM$ cosmological model with an energy equation of state, $P= c \omega(z) \rho$ and a $\Lambda CDM$ model. I considered a cosmological model for $\omega(z)=-1 +\alpha z$ then I tried to find the best $\alpha$. In this paper, we first calculate the detection rate of Swift/BAT for a cosmological model with the $ \omega CDM$ model. We use this probability density function to generate the redshift of LGRBs in our Monte-Carlo simulation. in a Monte Carlo simulation, we want to simulate $\tau = \tau_0 (1+z)$ for 1347 mock LGRBs and compare the histogram of $\tau$ for assumed cosmological model and observational histogram of $\tau$. Finally, $\chi^2$ minimization method is employed to determine the optimal value of $\alpha$ in the dark energy equation of state, $P= c \omega(z) \rho$, with $\omega(z)=-1+\alpha z$ . We showed that for the $\omega CDM$ model all values of $\alpha$ within $\alpha=[0, 0.16]$ range are considered acceptable within two standard deviations.

یکشنبه  16 دی 1403، ساعت 17:00

Sunday 5 January 2025 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3 /  

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Arefeh Alizadeh

Department of Physics, Sharif University of Technology

Dark Matter Phenomenology: Production Mechanisms and Freeze-In via Inverse Semi-Annihilation

 Abstract: Dark matter is a key part of modern cosmology and particle physics. Studying its evolution and properties helps us understand the universe’s large-scale structure, galaxy dynamics, and the fundamental particles that may exist beyond the Standard Model.

In this presentation, I will give an overview of the evidence supporting the existence of dark matter and the possible candidates proposed to explain these observations. Production mechanisms, including misalignment, thermal freeze-out, and freeze-in, will be discussed. I will then focus on the freeze-in mechanism, a well-motivated scenario for non-thermal dark matter production. As discussed in arXiv:2104.05684, through inverse semi-annihilation processes, the freeze-in mechanism can explain the current abundance of dark matter. The semi-production approach allows for larger coupling values compared to the usual freeze-in scenario by considering a small initial abundance of dark matter.

یکشنبه 9 دی 1403، ساعت 17:00

Sunday 29 December 2024 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Adeela Afzal

Department of Physics, Quaid-i-Azam University, Islamabad, Pakistan

Tracing the Cosmos with Stochastic Gravitational-Wave Background

Abstract: Hybrid inflation provides a rich framework for understanding the early universe’s dynamics and its connection to observable cosmic structures. This talk will explore the role of hybrid inflation in generating topological defects and the stochastic gravitational wave background, emphasizing model-building approaches to connect theoretical predictions with observations. I will discuss the potential origins of the signals detected in the NANOGrav 15-year dataset and how they relate to cosmic phenomena such as scalar-induced gravitational waves and cosmic strings. Furthermore, we will delve into the intriguing possibility of primordial black hole formation during hybrid inflation and its implications for current and future astrophysical observations.  I will also talk about weighted Morphology and its implications on topological defects. This presentation aims to bridge theoretical insights with observational data, shedding light on the intricate interplay between inflationary physics, gravitational waves, and primordial black holes.

یکشنبه 18 آذر 1403، ساعت 17:00

Sunday 8 December 2024 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3 /  

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Mahdiyar Mousavi-Sadr

School of Astronomy, Institute for Research in Fundamental Sciences (IPM)

 A statistical study of exoplanetary systems and the correlations between their parameters 

Abstract: The number of discovered exoplanets is increasing dramatically, so that over 5,500 exoplanets have been confirmed to date. This large number of exoplanets and advances in machine-learning techniques open new avenues for exploring and understanding the characteristics of worlds beyond our Solar system. In this study, we use machine learning approaches to analyze a data set comprising 770 planets, aiming to characterize their fundamental quantities. We classify the data into two main classes: ‘small’ and ‘giant’ planets. Furthermore, using different regression models, we try to uncover possible correlations between stellar and planetary parameters. Notably, our study reveals a noteworthy finding: there is a positive linear relation between the size of giant planets and the mass of their host stars, which might provide interesting insights into the formation and evolution theories of planets.

یکشنبه 11 آذر 1403، ساعت 17:00

Sunday 1 December 2024 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Armin Sadeghi

Department of Physics, University of Tehran

Collapse into regular black holes 

Abstract: In this talk, we explore the formation of regular black holes with de Sitter cores, from the gravitational collapse of a massive star based on a generalized Oppenheimer–Snyder collapse model. The collapse scenario leads to a class of general regular black holes with de Sitter cores. We will examine key properties of these black holes, including their horizons, energy conditions, and surface gravity.

یکشنبه  4 آذر 1403، ساعت 17:00

Sunday 24 November 2024 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Golshan Ejlali

School of Astronomy, Institute for Research in Fundamental Sciences (IPM)

 Investigating Millimeter Emission in Nearby Galaxies 

Abstract:D ust plays a crucial role in the interstellar medium of galaxies, influencing their thermal, chemical, and radiative properties. It absorbs and scatters starlight, leading to extinction and reddening effects, and re-emits the absorbed energy in the far-infrared. Dust also cools the interstellar medium by emitting radiation in infrared and submillimeter wavelengths and acts as a catalyst for molecular hydrogen formation, essential for star formation.  The IMEGIN project (Interpreting Millimeter Emission of Galaxies with IRAM and NIKA2) leverages the NIKA2 camera on the IRAM 30m telescope to explore millimeter properties of galaxies, focusing on dust emission beyond 500 µm to detect cold dust components. This project, led by Dr. Suzanne Madden and involving 14 European institutes in addition to IPM from Iran, aims to disentangle contributions from dust, synchrotron, and free-free emissions. High spatial resolution maps of these emissions will advance our understanding of star formation and dust evolution in galaxies. We utilized multi-wavelength data from Herschel, Spitzer, and Planck in infrared and submillimeter, and from VLA, Effelsberg and WSRT in radio regime to complement NIKA2 observations, constructing detailed spectral energy distributions (SEDs) for a diverse sample of galaxies. This enables the separation of different emission components and derivation of key physical parameters such as dust temperature, mass, and composition. We investigated the relationship between dust properties and galactic characteristics like star formation rate, and morphology, providing insights into dust evolution and galaxy evolution. We also suggest millimeter emission as a powerful extinction-free tracer of molecular gas across various galactic environments.

یکشنبه  27 آبان 1403، ساعت 17:00

Sunday 17 November 2024 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Ali Rostami

Department of Physics, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan

Black Holes as Catalysts: The Far-Reaching Effects of Black Hole Retention in Evolution of Star Clusters 

Abstract: Massive stars, upon exhausting their thermonuclear fuel, undergo gravitational collapse followed by supernova explosions, leaving behind black holes (BHs) as remnants. These explosions aren’t perfectly symmetrical, and the uneven ejection of mass imparts a “natal kick” to the newborn BH. The magnitude of these kicks remains a subject of debate, creating uncertainty about the initial population of BHs retained in star clusters. High natal kicks lead to the immediate ejection of BHs from their host clusters, while gentler kicks allow them to stay put, forming a sub-system of BHs right in the cluster’s heart. This BH sub-system (BHSub) acts like a bustling, dynamic factory at the cluster’s core, pumping energy into its surroundings and dramatically influencing its evolutionary path.

In this talk, I’ll first address the dynamical processes governing clusters harboring a BHSub, followed by an examination of the emergence and evolution of the dark cluster phase. But that’s not all – I’ll demonstrate how assuming low natal kicks for BHs and the subsequent formation of a BHSub in the cluster’s heart can provide explanations for several outstanding open questions regarding globular clusters:

1. The origin of high dark remnant fractions in Milky Way globular clusters
2. The dichotomy between metal-rich and metal-poor globular clusters in the Milky Way
3. The mysterious lack of metal-poor globular clusters in the inner regions of early-type galaxies

By the end, you’ll see just how far-reaching the effects of BH retention can be in the grand story of star cluster evolution.

یکشنبه  20 آبان 1403، ساعت 17:00

Sunday 10 November 2024 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest